AN-1112 DSBGA Wafer Level Chip Scale Package (Rev. AI)
13
1 SNVA009AI – September 1999 – Revised December 2019 Submit Documentation Feedback Copyright © 1999–2019, Texas Instruments Incorporated AN-1112 DSBGA Wafer Level Chip Scale Package Application Report SNVA009AI – September 1999 – Revised December 2019 AN-1112 DSBGA Wafer Level Chip Scale Package ABSTRACT This application note provides information on handling, assembly, and usage of the die-sized ball grid array (DSBGA) wafer chip scale package (WCSP). Contents 1 Introduction .................................................................................................................. 1 2 DSBGA Technology Description .......................................................................................... 2 3 Surface Mount Assembly Considerations ................................................................................ 8 4 PCB Layout ................................................................................................................... 9 5 Stencil Printing Process ................................................................................................... 10 6 Component Placement .................................................................................................... 10 7 Solder Paste, Reflow, and Cleaning ..................................................................................... 10 8 Rework....................................................................................................................... 11 9 Qualification ................................................................................................................. 11 10 Thermal Characterization ................................................................................................. 11 11 Conclusion .................................................................................................................. 11 List of Figures 1 Standard WCSP Cross Sections .......................................................................................... 3 2 PowerWCSP Cross Section ................................................................................................ 3 3 Embedded PicoStar (Left) and PicoStar SMT (Right) Cross Section................................................. 4 4 Tape and Reel Information (Example) .................................................................................... 5 5 WCSP ePOD Example...................................................................................................... 6 6 Laser Marking Example ..................................................................................................... 7 7 Typical WCSP Surface Mount Flow ...................................................................................... 8 8 PicoStar SMT Non-Solder Mask Defined (NMSD) Pad Geometry Recommendation ............................. 8 9 NSMD and SMD Pad Definition ........................................................................................... 9 List of Tables 1 MSL Classifications.......................................................................................................... 4 Trademarks PicoStar is a trademark of Texas Instruments. All other trademarks are the property of their respective owners. 1 Introduction This application note provides guidelines and recommendations for wafer chip scale packages (WCSP). WCSP is a package type that is completely processed in wafer form; and when singulated, the package is complete. In this document, the following references are included: • Package descriptions • Surface mount assembly considerations • PCB layout
Transcript of AN-1112 DSBGA Wafer Level Chip Scale Package (Rev. AI)
1SNVA009AI–September 1999–Revised December 2019Submit Documentation Feedback
Copyright © 1999–2019, Texas Instruments Incorporated
AN-1112 DSBGA Wafer Level Chip Scale Package
Application ReportSNVA009AI–September 1999–Revised December 2019
AN-1112 DSBGA Wafer Level Chip Scale Package
ABSTRACTThis application note provides information on handling, assembly, and usage of the die-sized ball gridarray (DSBGA) wafer chip scale package (WCSP).
Contents1 Introduction .................................................................................................................. 12 DSBGA Technology Description .......................................................................................... 23 Surface Mount Assembly Considerations ................................................................................ 84 PCB Layout ................................................................................................................... 95 Stencil Printing Process ................................................................................................... 106 Component Placement .................................................................................................... 107 Solder Paste, Reflow, and Cleaning ..................................................................................... 108 Rework....................................................................................................................... 119 Qualification ................................................................................................................. 1110 Thermal Characterization ................................................................................................. 1111 Conclusion .................................................................................................................. 11
List of Figures
1 Standard WCSP Cross Sections .......................................................................................... 32 PowerWCSP Cross Section................................................................................................ 33 Embedded PicoStar (Left) and PicoStar SMT (Right) Cross Section................................................. 44 Tape and Reel Information (Example) .................................................................................... 55 WCSP ePOD Example...................................................................................................... 66 Laser Marking Example..................................................................................................... 77 Typical WCSP Surface Mount Flow ...................................................................................... 88 PicoStar SMT Non-Solder Mask Defined (NMSD) Pad Geometry Recommendation ............................. 89 NSMD and SMD Pad Definition ........................................................................................... 9
List of Tables
1 MSL Classifications.......................................................................................................... 4
TrademarksPicoStar is a trademark of Texas Instruments.All other trademarks are the property of their respective owners.
1 IntroductionThis application note provides guidelines and recommendations for wafer chip scale packages (WCSP).WCSP is a package type that is completely processed in wafer form; and when singulated, the package iscomplete. In this document, the following references are included:• Package descriptions• Surface mount assembly considerations• PCB layout
DSBGA Technology Description www.ti.com
2 SNVA009AI–September 1999–Revised December 2019Submit Documentation Feedback
Copyright © 1999–2019, Texas Instruments Incorporated
AN-1112 DSBGA Wafer Level Chip Scale Package
• Thermal characterization
2 DSBGA Technology DescriptionDie-sized ball grid array (DSBGA) is the broader term for WCSP technologies with the following features:• Package size equal to die size• Smallest footprint per I/O count• Interconnect layout available in 0.3-mm, 0.35-mm, 0.4-mm, or 0.5-mm pitch• No interposer between the silicon IC and the printed circuit board• TI DSBGA solutions include Standard WCSP, PicoStar™, and PowerWCSP• TI DSBGA products are designed and tested to ensure excellent board-level thermal cycling reliability
without the need for underfill in intended applications. If a customer chooses to underfill a DSBGAproduct, TI recommends following the guidelines below to maximize reliability.
• The underfill fillet should extend partially up the die edges. Underfill that ends at the bottom (ball side)of the die will degrade reliability.
• The underfill should have a CTE closely matched to the CTE of the solder interconnect.• The underfill should have a Tg above the expected maximum exposure temperature.
Typical DSBGA products have solder bumps located on the active side of silicon IC. The DSBGAmanufacturing process steps include the following:• Standard wafer fabrication process• Wafer re-passivation• Deposition of solder bumps on I/O pads• Backgrinding• Application of protective encapsulation coating• Testing using wafer sort platform• Laser marketing• Singulation• Packing in tape and reel
The package is assembled on PCB using standard surface mount assembly techniques (SMT).
2.1 Standard WCSPPackages are available in standard bump arrays ranging from 2 x 2 to 11 x 11. Standard pitch options are0.3, 0.35, 0.4, and 0.5 mm with package heights ranging from 0.35 to 0.55 mm. Please contact a TI salesrepresentative for available combinations.
The cross section drawings in Figure 1 show two types of standard WCSP bumping technologies.
www.ti.com DSBGA Technology Description
3SNVA009AI–September 1999–Revised December 2019Submit Documentation Feedback
Copyright © 1999–2019, Texas Instruments Incorporated
AN-1112 DSBGA Wafer Level Chip Scale Package
Figure 1. Standard WCSP Cross Sections
2.2 Power WCSPPowerWCSP is an enhanced WCSP package capable of having low package profile (maximum 0.3-mmthickness). The unique bump structure depicted below improves thermal performance and current carryingdensity compared to standard WCSP packages.
Figure 2. PowerWCSP Cross Section
2.3 PicoStarPicoStar is another type of DSBGA solution TI provides, including embedded PicoStar and PicoStar SMT.Embedded PicoStar gives the customer the ability to insert it into a substrate. This increases the versatilityof the package for various applications including embedded and system in package (SiP) solutions.PicoStar SMT provides the smallest possible package height, and is applicable to smaller packages.Please contact a TI sales representative for more information regarding.
DSBGA Technology Description www.ti.com
4 SNVA009AI–September 1999–Revised December 2019Submit Documentation Feedback
Copyright © 1999–2019, Texas Instruments Incorporated
AN-1112 DSBGA Wafer Level Chip Scale Package
Figure 3. Embedded PicoStar (Left) and PicoStar SMT (Right) Cross Section
2.4 Attributes Applicable for All Technologies
2.4.1 MSL/StorageThe Moisture Sensitivity Level (MSL) indicates the floor life of the component kept at or below conditionsof 30°C and 60% RH. All DSBGA packages are ranked as level 1. Refer to JEDEC for conditions.
Table 1. MSL Classifications
LEVEL FLOOR LIFE1 Unlimited2 1 year2a 4 weeks3 168 hours4 72 hours5 48 hours5a 24 hours6 Time on label
2.4.2 Tape and Reel InformationDSBGA units are contained within Tape and Reel (T and R) configurations, which are intended to protectdevices from damage during transportation and storage. Figure 4 is an example of T and R dimensionsprovided in the data sheet of each device.
www.ti.com DSBGA Technology Description
5SNVA009AI–September 1999–Revised December 2019Submit Documentation Feedback
Copyright © 1999–2019, Texas Instruments Incorporated
AN-1112 DSBGA Wafer Level Chip Scale Package
Figure 4. Tape and Reel Information (Example)
2.4.3 ePODFigure 5 illustrates an example of an enhanced package outline drawing (ePOD). Refer to the TI datasheet for device specific information.
DSBGA Technology Description www.ti.com
6 SNVA009AI–September 1999–Revised December 2019Submit Documentation Feedback
Copyright © 1999–2019, Texas Instruments Incorporated
AN-1112 DSBGA Wafer Level Chip Scale Package
Figure 5. WCSP ePOD Example
2.4.4 Laser Marking DecoderLaser marking provides traceability information of where the device is manufactured. Please note allinformation may not be included in the markings, depending on die size. Standard laser marking maycontain, but is not limited to:• Pin 1 identification• Commercial product name• Codes for traceability, wafer fabs, testing, and finishing production locations• Country where the product is assembled
Figure 6 shows an example of laser marking.
www.ti.com DSBGA Technology Description
7SNVA009AI–September 1999–Revised December 2019Submit Documentation Feedback
Copyright © 1999–2019, Texas Instruments Incorporated
AN-1112 DSBGA Wafer Level Chip Scale Package
Figure 6. Laser Marking Example
Surface Mount Assembly Considerations www.ti.com
8 SNVA009AI–September 1999–Revised December 2019Submit Documentation Feedback
Copyright © 1999–2019, Texas Instruments Incorporated
AN-1112 DSBGA Wafer Level Chip Scale Package
3 Surface Mount Assembly ConsiderationsDSBGA surface mount assembly operations include:• Printing solder paste onto a PCB• Component placement using standard pick and place equipment• Solder reflow and cleaning (depending on flux type)
Advantages of DSBGA during SMT assembly include:• Standard SMT pick and place equipment• Standard reflow process
3.1 WCSP Surface Mount Flow
Figure 7. Typical WCSP Surface Mount Flow
3.2 Special Considerations for PowerWCSPSMT using solder paste for PowerWCSP should follow recommendations for Standard WCSP.Optimization of the SMT process for PowerWCSP is required to avoid issues, like tilting. Contact a TIrepresentative for more information regarding PowerWCSP.
3.3 Special Considerations for PicoStar SMTGeneral PCB board and stencil design recommendations specific for PicoStar SMT are in Figure 8.Contact a TI representative for more information.
Figure 8. PicoStar SMT Non-Solder Mask Defined (NMSD) Pad Geometry Recommendation
www.ti.com PCB Layout
9SNVA009AI–September 1999–Revised December 2019Submit Documentation Feedback
Copyright © 1999–2019, Texas Instruments Incorporated
AN-1112 DSBGA Wafer Level Chip Scale Package
4 PCB Layout
4.1 NMSD versus SMDTwo types of PCB land patterns are used for surface mount packages:1. Non-solder mask defined (NSMD)2. Solder mask defined (SMD)
Figure 9. NSMD and SMD Pad Definition
1. The NSMD configuration is preferred due to its tighter control of the copper etch process and areduction in the stress concentration points on the PCB side compared to SMD configuration.
2. A copper layer thickness of less than 1 oz is recommended to achieve higher solder joint stand-off. A 1oz. (30 micron) or greater copper thickness causes a lower effective solder joint stand-off, which cancompromise solder joint reliability.
3. For the NSMD pad geometry, the trace width at the connection to the land pad should not exceed 2/3of the pad diameter.
4.2 PCB Pad Geometry RecommendationRefer to device data table and TI representative for more information.
4.3 FinishOrganic solderability preservative coating (OSP) as well as ENIG (Electroless Nickel Immersion Gold)finish is preferred.• For ENIG (Electroless Nickel Immersion Gold), gold thickness must be less than 0.2 microns to avoid
solder joint embrittlement.• The fan-out for the traces should be symmetrical across X and Y directions to avoid part rotation due
to surface tension of solder.• HASL (Hot Air Solder Leveled) board finish is not recommended.
PCB Layout www.ti.com
10 SNVA009AI–September 1999–Revised December 2019Submit Documentation Feedback
Copyright © 1999–2019, Texas Instruments Incorporated
AN-1112 DSBGA Wafer Level Chip Scale Package
4.4 ViasFor PCB layouts employing via-in-pad structures (micro-via), NSMD pad definition should be used, sincethis ensures adequate wetting area on the copper pads, hence a better joint. It is also recommended thatthe wall thickness of the microvias is a minimum of 15 microns. Additionally, it is recommended that 'offset'vias be used when microvias are required for routing on the PCB.
5 Stencil Printing Process• Use laser cutting followed by electro-polishing for stencil fabrication. Chemical etch is not
recommended.• If possible, offset apertures from land pads to maximize separation and minimize possibility of bridging
for DSBGA packages with less than 10 bump counts with small bump size. No print offset is requiredfor higher bump counts and larger bump size.
• Use Type 3 paste (25 to 45 micron particle size range) or finer solder paste for printing.• Using Type 2 or Type 1 paste (Particle size > 45 μm) is not recommended.
6 Component PlacementStandard pick-and-place machines can be used for placing the DSBGA. Either one of the followingmethods can be used for recognition and positioning.• Vision system to locate package silhouette• Vision system to locate individual bumps. It is recommended that side-lighting on the vision system of
the pick-and-place machine be used when attempting to use individual bump recognition.
Other recommendations for DSBGA placement:• It is preferable to use IC placement/fine pitch placement machines over chip-shooters for better
accuracy.• DSBGA solder bumps self-align when placed at an offset due to self-centering nature of solder bumps.• Though DSBGA can withstand a placement force of up to 1 kg for 0.5 seconds, little or no force needs
to be exerted during placement. It is recommended that bumps be immersed into the solder paste onthe PCB to greater than 20% of paste block height.
7 Solder Paste, Reflow, and Cleaning• DSBGA is compatible with industry standard reflow.• DSBGA is qualified for up to three reflow operations (260°C peak) per J-STD-020.• Use of Pb-free DSBGA with eutectic solder paste is not recommended. Such an application can result
in assemblies that will not meet desired reliability standards.• Type 3 (25 to 45 µm particle size range) or finer solder paste is recommended, while type 2 or type 1
is not recommended.• It is recommended to match solder paste alloy and assembly process with the component bumps alloy
(for example, Pb-free paste and process to be used with Pb-free components).
www.ti.com Rework
11SNVA009AI–September 1999–Revised December 2019Submit Documentation Feedback
Copyright © 1999–2019, Texas Instruments Incorporated
AN-1112 DSBGA Wafer Level Chip Scale Package
8 ReworkThe key features for the DSBGA rework are the following:1. Rework procedure used is identical to the one used for most BGA and CSP packages.2. Rework reflow process should duplicate original reflow profile used for SMT assembly.3. Rework system should include localized convection heating element with profiling capability, a bottom
side pre-heater and a part pick and placer with image overlay.4. A DSBGA should not be reused.
9 QualificationTI qualifies all devices to JEDEC reliability standards. Component level tests are performed such as HighTemperature Operating Life, Biased HAST (highly accelerated stress test), Unbiased HAST, andTemperature Cycle and High Temperature Storage Bake. Board level thermal cycling and board level droptest are also performed. Refer to JEDEC for conditions and consult TI representative for specific devicereliability data.
10 Thermal CharacterizationThermal performance of DSBGA packages are assessed using low effective thermal conductivity testboards per EIA/JESD51-3. The performance of the DSBGA product depends on product die size andapplication (PCB layout and design), and the details of Theta JA values are available in product datasheets at www.ti.com. For more information about traditional and new thermal metrics, see theSemiconductor and IC Package Thermal Metrics application report.
11 ConclusionTexas Instruments DSBGA devices are introduced in this application note. Key features of this productinclude:• PCB space saving: package size is equal to die size and reduced thickness and weight.• Enhanced electrical performance: shorter electrical parts than in standard plastic packages improves
electrical performance
Adhering to the recommendations and references in this document ensures high quality and consistentassembly yield.
Revision History www.ti.com
12 SNVA009AI–September 1999–Revised December 2019Submit Documentation Feedback
Copyright © 1999–2019, Texas Instruments Incorporated
Revision History
Revision HistoryREVISION DATE DESCRIPTION
December 2004 Replaced Table 6. Current Figure 6 was Figure 8. Replaced Figure 7 and Figure 8. ModifiedDo's and don'ts tables.
August 2005 Added 0.4 mm pitch information.
September 2005 Added “Large Dome Bump” paragraph to the Surface Mount Assembly Considerationssection.
August 2006 General review, minor edits.October 2006 Modify 0.5 mm Pitch (0.3 mm dia) Do's and Don'tsDecember 2006 Add a bullet to the Solder Paste Reflow and Cleaning section.March 2007 Modify Table 1. Recommended PCB Pad GeometryJune 2007 Update Figure 1. Remove 36 bump references. Replace Figure 4. Update all Do's and Don'tsDecember 2007 Add 0.3 mm pitch informationSeptember 2009 Add in 0.4 mm pitch 64 bumps DSBGA package informationJanuary 2010 Add dome bump, ultra-thin and extreme-thin package information.
September 2011 Added 0.35 mm pitch info to Recommended PCB pad and Recommended Stencil Aperturestables.
April 2012 Added more 0.35 mm pitch information.May 2012 Insert Appendix A. Modify Appendix B.
March 2015
Removed “Use of underfill is not recommended” from section 1 and 8.Added “The use of an underfill with a CTE matching the solder will enhance the board levelperformance” to section 1. Added “Refer to Application Report, Forward/BackwardCompatibility snoa923 for details” to section 1.Corrected figure 1 from “DSBGA 4-30 Bump” to “DSBGA 4-25 Bump” Updated table 3.Changed “micro SMD” to “DSBGA” in section 4, 7, and 11.Changed “Ni-Gold board finish” to “Electroless Nickel Immersion Gold “
August 2015
TI DSBGA products are designed and tested to ensure excellent board-level thermal cyclingreliability without the need for underfill in intended applications. If a customer chooses tounderfill a DSBGA product, TI recommends following the guidelines below to maximizereliability.
– The underfill fillet should extend partially up the die edges. Underfill that ends at thebottom (ball side) of the die will degrade reliability.– The underfill should have a CTE closely matched to the CTE of the solder interconnect.– The underfill should have a Tg above the expected maximum exposure temperature.
May 2019 Added “PowerWCSP” section to document.December 2019 Edited application report for clarity.
IMPORTANT NOTICE AND DISCLAIMER
TI PROVIDES TECHNICAL AND RELIABILITY DATA (INCLUDING DATASHEETS), DESIGN RESOURCES (INCLUDING REFERENCEDESIGNS), APPLICATION OR OTHER DESIGN ADVICE, WEB TOOLS, SAFETY INFORMATION, AND OTHER RESOURCES “AS IS”AND WITH ALL FAULTS, AND DISCLAIMS ALL WARRANTIES, EXPRESS AND IMPLIED, INCLUDING WITHOUT LIMITATION ANYIMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT OF THIRDPARTY INTELLECTUAL PROPERTY RIGHTS.These resources are intended for skilled developers designing with TI products. You are solely responsible for (1) selecting the appropriateTI products for your application, (2) designing, validating and testing your application, and (3) ensuring your application meets applicablestandards, and any other safety, security, or other requirements. These resources are subject to change without notice. TI grants youpermission to use these resources only for development of an application that uses the TI products described in the resource. Otherreproduction and display of these resources is prohibited. No license is granted to any other TI intellectual property right or to any thirdparty intellectual property right. TI disclaims responsibility for, and you will fully indemnify TI and its representatives against, any claims,damages, costs, losses, and liabilities arising out of your use of these resources.TI’s products are provided subject to TI’s Terms of Sale (www.ti.com/legal/termsofsale.html) or other applicable terms available either onti.com or provided in conjunction with such TI products. TI’s provision of these resources does not expand or otherwise alter TI’s applicablewarranties or warranty disclaimers for TI products.
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265Copyright © 2019, Texas Instruments Incorporated
